DEGREE PROJECT IN MECHANICAL ENGINEERING, SECOND CYCLE, 30 CREDITS STOCKHOLM, SWEDEN 2019 Conceptual Design Study of a Foil-Trailer to AUV 62-AT JACOB ZEIDLER KTH ROYAL INSTITUTE OF TECHNOLOGY SCHOOL OF ENGINEERING SCIENCES Conceptual Design Study of a Foil-Trailer to AUV 62-AT JACOB ZEIDLER Master in Naval Architecture Date: September 23, 2019 Supervisor: Mateo Perrone Examiner: Stefan Hallström School of Engineering Sciences Host company: Försvaretsmaterielverk (Swedish Defence Materiel Administration) Swedish title: Konceptuelle design studie av en bärplans-trailer för AUV 62-AT iii Abstract The Swedish Navy has been using the AUV62-AT for submarine hunting training success- fully for a while and it has been found that the biggest drawback is the transport which is very resource draining. The Swedish Defence Materiel Administration was given the task to solve this and a hydrofoiling-trailer was seen as a potential solution. This thesis will present the design process of the foil-trailer as well as issues found and how theses were mitigated, to produce a viable design. To develop the final design both current use of hydrofoil vessels and further adaptions needed for this applications were investigated. The project was done in collaboration with Simon Källerfelt Korall, who has during the project investigated in detail the foil-trailer’s roll stability, presents this in "The development of a foiling trailer for transport of the AUV62-AT"[1], which deals with how the experimental- and model results lines up. The result is a final design of a foil-trailer which is constituted of several sub-systems that has been found to improve the overall concept. It was concluded that the concept was viable and if further developed it can be used as a great method of saving time when deploying the AUV62-AT. iv Sammanfattning Svenska flottan har länge använt AUV62-AT för ubåtsjaktträning, det har upptäckts att den största nackdelen med användandet är att transporten är resurskrävande. Försvarets materielverk har därför fått uppdraget att utveckla ett sätt att transportera den, en bärplans- trailer har blivit förslagen som en möjlig lösning. Den här uppsatsen presenterar designprocessen samt vilka utmaningar samt hur dessa kan lösas. För att utveckla en välfungerande design har både tidigare användande av bärplans- båtar så väl som anpassningar av dessa undersökts. Detta projekt är gjort i samarbete med Simon Källerfelt Korall, som har under arbetes gång väl genomfört en studie om bärplans- trailerns rullningsstabilitet, detta är presenterat i rapporten, "Utveckling av en bärplanstrai- ler för transport av AUV62-AT"[1] som hanterar hur väl den skapade modellen överens- stämmer med experimentresultat. Resultatet av studien är en slutgiltig konstruktion av en bärplans-trailer bestående av flera delsystem som kommer förbättra konceptet. Slutsatsen kunde dras att konceptet är gång- bart och om vidare utvecklat kan det spara mycket tid i användandet av AUV62-AT. v Acknowledgements I would like to foremost thank Simon Källerfelt Korall for a great collaboration. Moreover, I would like to thank the project commissioners Matteo Peroni and Johan Wahrén at the Swedish Defence Materiel Administration and the examiners Stefan Hallström and Ivan Stenius at the Royal Institute of Technology for an interesting project and great advise during the project. I would also like to thank friends and family for support during the project. vi Forewords The study was done at the KTH department of Naval Architecture and was supervised by the Swedish Defence Material Administration and Stefan Hallström, associate professor in lightweight structures. The project was done in collaboration with Simon Källerfelt Korall, who focused on the foil-water performance predictions in normal operations [1], while the model design work and the testing was done jointly. This report presents the focus area of the author; the in depth design process and the op- timization of the final concept. Furthermore, the findings from the overall process are presented. This includes several investigations and mitigation of potential problems, all to optimize the functionality of the final product. Finally, the complete project is presented in two separate reports and a complete picture of the project is only obtained trough reading both reports. Contents 1 Introduction 1 1.1 Background . .1 1.2 Aims . .3 1.2.1 Project Objective . .3 1.2.2 Thesis Objective . .4 1.2.3 Method . .4 2 Hydrofoil Technology 5 2.1 Working Principles . .8 2.2 Important Considerations . 10 2.2.1 Cavitation . 10 2.2.2 Ventilation . 12 2.3 Stability . 12 2.3.1 Longitudinal Stability . 12 2.3.2 Roll Stability . 13 2.4 Hydrofoil Types . 13 2.4.1 Surface Piercing Hydrofoil . 14 2.4.2 Submerged Hydrofoil . 14 2.4.3 Wing Profile . 15 2.4.4 Control System . 17 2.5 Structural Considerations . 18 3 Design Evaluation 19 3.1 Intended Use . 19 3.2 Connection to RIB . 20 3.3 Wing Profile . 20 3.3.1 Wing Profile Investigation . 21 3.4 Control System . 21 3.5 Foil and Struts Arrangement . 25 3.6 Hydrofoil Type . 26 3.7 Stability . 27 4 Scale Testing 29 4.1 Purpose . 29 4.2 Experimental Setup . 29 4.3 Tested Model . 30 4.4 Results . 32 5 Results and Final Design 34 5.1 Joint . 34 5.2 Ease of Use . 34 5.2.1 Rope System . 35 5.2.2 Modular System . 36 5.3 Structural . 36 vii viii CONTENTS 5.3.1 Grounding Protection . 36 5.3.2 Dimensioning Load Case . 37 6 Conclusion 38 Bibliography 40 A Appendix 42 A.1 Cavitation . 42 A.2 Weight of different foil configuration . 44 1 Introduction This document serves as a master thesis report for the Master of Science program in Naval Architecture at KTH, Royal Institute of Technology. The project consists of a literature study, a conceptual design study, a scale test, and a presentation of the final design. As part of the project a foil-trailer will be developed to use for transporting bigger torpedo shaped bodies and is specially designed for transporting the AUV-62 AT. The project was performed in collaboration with FMV (the Swedish Defence Materiel Administration) and KTH, this report only presents parts of the project. For the full picture of the project, Si- mon Källerfelt Korall’s report must be read as well. This thesis will present and discuss the design process and the choices made throughout the project, it will also serve as a full presentation of the product which was designed in the project. 1.1 Background With the recent improvement of information technology, it has been made possible to make underwater vehicles which are not in need of direct control from humans, hence it is possible to make the underwater vehicles more efficient. The Autonomous Underwater Vehicles (AUVs) are both cheaper to make and operate than bigger, manned ones, which has caused a big increase in the number of AUVs on market. Since AUVs might be a tool for smart warfare in the future, most countries has strived to acquire in-house exper- tise within the subject. In Sweden this has lead to the Swedish Defense Research Agency (FOI), the Swedish Armed Forces, the Swedish defense agency (FMV), and Saab Dynam- ics to embark on a joint effort to design a modular AUV that is based on the Swedish torpedo 62 hulls. Using the previously designed hull means more efforts can be spent on other parts of the AUV, saving money and time. This development has resulted in several AUVs with two main purposes; mine hunting and submarine hunting training. For mine hunting one needs a way to scan the water with high resolution. Both SAP- PHIRES (Synthetic Aperture Processing High Resolution Sensor) and AUV 62-MR (Mine Reconnaissance) does this using a synthetic multi-beam sonar array that is then used for mapping the sea floor of the Baltic to scan for mines. It has been proven to be a valuable asset to the Swedish Armed Forces when performing tasks such as finding World War two mines, dumped ammunition, and assisting when the Swedish Coast Guard in a miss- ing person incidents. The search area can be in the magnitude of a couple km2 and the visibility of divers could be around a few dm [2]. To be able to practice submarine hunting operations, it is desirable to have an AUV that can act and appear as several different submarine in the world. This is done by using an AUV with a quiet engine so the own signature is very small, therefore, allowing it to send out acoustic images using both passive and active signatures to the search party. AUV62- AT (Acoustic Target) can be seen by several search parties at the same time allowing it to 1 2 CHAPTER 1. INTRODUCTION (a) Found Drown Victim [2] (b) Launch and recovery on 30m Fårösund [2] Figure 1.1: Operation of AUV 62 work as a submarine would have. The two main advantages compared to practicing with the real submarine are that it can act and look like any submarine (not just the ones the country has) and it frees up the time from the submarine to do other missions during that time[3]. The AUV family is well proven and therefore often used. It saves resources but has a finite battery time hence it is transported dead, often using a surface vessel. It needs to be done in a quick, safe and cheap way. At the moment the two main methods used for transporta- tion are either with a 30m vessel (see figure1.1b) or with a 10m RIB. On the bigger vessel the AUVs are being lifted up on the deck by a crane, which allows the vessel to be able to operate normally, while the weight of the AUV is small in compassion to the vessel.